Theorem 2.8  
Let \((L_{ij}^{\sigma })_{1 \le i,j \le d_{\sigma }}\)  be the matrix of \(L^{\sigma }\)  in an orthonormal basis \((\xi _{i})_{i=1}^{d\sigma }\)  of \(H_{\sigma }.\)  Then, (see [1]}, [2]}, [3]}, [4]}),
\( \int _{K}L_{ij}^{\sigma }(t)\overline{L_{lm}^{\sigma }}(t)d \nu (t) & = & \dfrac{\delta _{il} \delta _{jm}}{d_{\sigma } }\) 
